Study of curing of layered silicate/trifunctional epoxy nanocomposites by means of FTIR spectroscopy

A study was conducted on the curing process of a nanocomposite consisting of a trifunctional epoxy resin, a hardener containing reactive primary amine groups, and montmorillonite (MMT) nanoparticles, previously treated with octadecyl ammonium. Three levels of MMT content were used: 2, 5, and 10%. The curing was carried out following the cycle: 4 h at 100°C, 2 h at 150°C, and 2 h at 200°C. Isothermal trials were also considered at three levels (120, 150, and 200°C) to conduct a kinetic study. The curing conversion was determined by FTIR spectroscopy by selecting the suitable bands for epoxide and primary amine functional groups. The study demonstrated that the MMT nanoparticles accelerate the curing process, especially at the initial stages of the thermal cycle, being this influence quasi negligible at the end of the cycle. Curing conversions were also evaluated by differential scanning calorimetry and compared to those obtained by FTIR spectroscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

联苯酚醛环氧树脂固化动力学及热性能研究

以4,4'-二氨基二苯砜(DDS)为固化剂,采用非等温示差扫描量热法(DSC)研究了联苯酚醛环氧树脂(BPNE)的固化动力学。通过外推法确定了体系的固化工艺。采用Kissinger、Ozawa法计算出固化体系的表观活化能,根据Crane理论计算得到该体系的固化反应级数。采用DSC,热重分析(TGA)研究了固化物的耐热性。结果表明:BPNE的固化工艺为160℃/2h+200℃/2h+230℃/2h;固化反应的活化能约为61.86kJ/mol,指前因子为5.27×105min-1,反应级数为1.1;玻璃化转变温度(Tg)为167℃,其10%热失重温度为398.1℃,800℃残炭率为29.37%,与双酚A环氧树脂/DDS固化物相比,分别提高了22℃,11.71%。     

Preparation and curing kinetics of bisphenol A type novolac epoxy resins

A bisphenol A type novolac resin (Bis‐ANR) was synthesized from bisphenol A and formaldehyde; the resulting novolac was epoxidized to generate a bisphenol A type novolac epoxy resin (Bis‐ANER). The chemical structures of Bis‐ANR and Bis‐ANER were confirmed by ¹H‐NMR spectroscopy and IR spectroscopy; the molecular weights and molecular weight distributions were determined by gel permeation chromatography. In addition, the curing process of Bis‐ANER with 4,4′‐diaminodiphenyl sulfone was studied in both dynamic and isothermal modes with differential scanning calorimetry. The dynamic curing kinetic analysis was evaluated with both the Kissinger and Flynn–Wall–Ozawa methods, and the curing activation energy values were obtained. The isothermal curing reaction exhibited autocatalytic behavior, and the curing kinetics were described with the Kamal kinetics model, which accounted for both the autocatalytic and diffusion‐control effects. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 858–868, 2006     

水性环氧树脂固化剂研究进展

介绍了水性环氧固化剂改性原理、改性方法以及国内外水性环氧固化剂的研究进展。     

环氧粉末涂料的固化动力学和固化工艺的研究

采用非等温示差扫描量热法(DSC)研究了E-12/双氰胺(固化剂)和E-12/双氰胺/2-甲基咪唑(促进剂)体系的固化反应动力学。采用Kissinger法和Crane公式对DSC数据进行处理,获得了固化反应动力学参数,应用热重分析(TGA)研究了固化产物的热稳定性。结果表明:双氰胺、2-甲基咪唑的最佳用量分别为环氧树脂质量的4%和0.4%,最佳固化条件为160℃/15min。E-12/双氰胺体系和E-12/双氰胺/2-甲基咪唑体系的表观活化能分别为105.12kJ/mol和70.62kJ/mol,固化反应级数n=0.92。起始分解温度约为410℃,促进剂2-甲基咪唑的加入对体系热稳定性没有影响。     

An interpenetrated system based on a tetrafunctional epoxy resin and a thermosetting bismaleimide: Structure–properties correlation

The kinetics and mechanism of the curing process of a thermosetting blend formed by tetraglycidyl-4,4′-diaminodiphenyl methane and N,N′-bismaleimido-4,4′-diphenyl methane (BMI) cured in the presence of 4,4′-diaminodiphenyl sulfone, was investigated in detail by Fourier transform infrared spectroscopy. Information on the molecular structure of the network formed upon curing was derived. Dynamic-mechanical measurements on dry samples indicated an interpenetrated polymer network-like structure. Sorption measurements at 70°C showed a reduction of the water uptake at equilibrium in the presence of substantial amounts of BMI in the system (43.5% body weight). Finally, the dynamic-mechanical analysis of wet samples demonstrated a reduction of the plasticizing efficiency of the absorbed water in the presence of BMI. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1029–1042, 1998     

新型含磷环氧树脂的合成及其反应动力学研究

将9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)与邻甲酚醛环氧树脂进行加成反应制得了含磷环氧树脂,并用FT-IR和NMR对其结构进行了表征,确认了该含磷环氧树脂的结构。采用DSC分析方法研究了DOPO与邻甲酚醛环氧树脂的反应动力学,得到两者反应的表观活化能Eα为53.457kJ/mol,反应级数n为0.93。     

新型环氧树脂胶粘剂的固化动力学研究

在不同升温速率下采用非等温差示扫描量热（DSC）技术对一种新型改性环氧树脂胶粘剂的固化反应过程进行了跟踪,并利用Kissinger、crane方程以及Arrhenius方程对该固化反应进行了动力学分析。结果表明,该固化反应的活化能为59.18kJ／mol,反应级数为0．89;结合Dsc谱图确定其固化工艺为130℃／1h＋150℃／2h＋175℃／3h。     

Effect of amino-polycarbonate on the curing kinetics and morphology of epoxy resin

The curing kinetics and the glass transition behavior of amino-polycarbonate with diglycidyl ether of bisphenol-A epoxy resin systems were studied by differential scanning calorimetry (DSC). The ASTM E-698 method was chosen to determine the kinetics parameters of the curing reaction, including the activation energy, preexponential factor, rate constant, and 60-min half-life temperature. The amino-polycarbonate was able to accelerate the curing reaction, reduce the apparent active energy, and decrease T_g of the systems. A homogeneous amino-polycarbonate/epoxy resin network was observed in scanning electron microscopy (SEM) pictures. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 833–838, 2001     

Molecular orientation in novolac cured epoxy resins as studied by rheo-optical FTIR spectroscopy

The molecular orientation and relaxation behavior was studied by rheooptical FTIR spectroscopy during the uniaxial deformation of epoxy resins prepared from the diglycidyl ether of butanediol and novolacs on the basis of bisphenol A. The investigation of orientation phenomena was performed in both the rubbery and the glassy state of the epoxies. Results are discussed with regard to the respective mechanism of deformation. Moreover, the effect of temperature, strain rate, and the molecular weight of the novolacs used on the orientation behavior and the mechanical properties was studied. A significant influence of these parameters on the molecular deformation behavior was observed. The reversibility of the orientation at temperatures above and below the glass transition temperature was examined. Epoxy films were subjected to successive loading–unloading cycles including elongation, relaxation, and annealing. The investigations show that the orientation is completely reversible in the rubbery state, but it is only partly reversible below the glass temperature. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 247–259, 1998     

腰果酚缩醛胺与环氧树脂的固化反应动力学的研究

在不同升温速率下,用差示扫描量热分析(DSC)研究了腰果酚缩醛胺固化剂(PCD)与环氧树脂的固化反应动力学。通过Kissinger、Crane方程和等转化率的方法求得了其表观活化能E=39.89kJ/mol,固化反应级数n=0.906。     

聚氨酯柔性固化剂/环氧体系固化动力学及机理

通过不同升温速率下示差扫描量热分析(DSC)研究了自制的聚氨酯柔性固化剂ATPU/环氧树脂E-44体系的固化反应动力学及机理。通过Kissinger和Crane方程求解了表观活化能和反应级数等动力学参数,并运用该参数研究了固化反应速率常数、固化反应速率、固化度等的变化规律及影响因素。通过反应级数的研究证明了固化反应为一复杂反应,不同的固化交联反应同时发生,但主要进行的是伯氨基及仲氨基与环氧基之间的反应,该类反应使得体系得以固化。     

环氧电工塑料的固化反应动力学研究

以双马来酰亚胺(BMI)/二氨基二苯砜(DDS)为组合固化剂,采用非等温示差扫描量热法(DSC)研究了邻甲酚醛环氧树脂(ECN)/DDS/BMI三元体系的固化反应动力学,用Kissinger法和Crane公式进行DSC数据处理,获得了固化反应动力学参数,并建立了固化动力学模型,同时结合红外光谱分析探讨了该体系的反应机理。结果表明,ECN/DDS/BMI体系固化反应级数n=0.93;表观活化能Ea=58.2 kJ/mol,与ECN/DDS体系相差很小,BMI的加入对体系的固化工艺影响不大,ECN/DDS/BMI体系的固化动力学模型与ECN/DDS体系相似。     

A new method to improve the stability,tensile strength,and heat resistant properties of shape‐memory epoxy resins: Two‐stages curing

In this article, we design a new thermal curing method: two‐stage curing. The purpose of using this approach is to maintain the excellent shape‐memory property of epoxy resin system after first stage curing, and the material can be folded in small size to storage or transportation and recovery its original shape commodiously by heating temperature. Then, after second stage curing, the stability, glass transition temperature(T_g), and tensile strength of material can be improved effectively. For this aim, a series of mixtures have been prepared. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), tensile test, scanning electron microscope (SEM), dynamic mechanical analysis (DMA), and fold‐deploy shape‐memory test have been used to characterize the feasibility of two‐stage curing process, curing degree, tensile strength, morphology, thermodynamic properties, and shape‐memory performance of these polymers. DSC results show that two independent curing stages can be achieved successfully. Tensile tests and DMA results suggest that tensile strength and heat resistance have been improved after the second curing stage. SEM results reveal that the addition of latent curing agent do not change the fracture mechanism. Furthermore, the fold‐deploy shape‐memory tests prove that the composites after first stage curing possess eximious shape‐memory property. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39882.     

Dynamic modeling of curing process of epoxy prepreg

The dynamic curing process was studied by using differential scanning calorimetry (DSC) and modeled by two methods. One was based on the Kissinger and Ozawa approach, in which the activation energy was taken as a constant for all the heating rates. The whole curing process was modeled with two cure reactions. Reaction 1 exhibited the behavior of the autocatalytic reaction, whereas Reaction 2 was the nth order reaction. The effect of heating rate on the preexponential factor A₁ of Reaction 1 was apparent. As the heating rate increased, the A₁ decreased. There was no significant effect of heating rate on the preexponential factor A₂ of Reaction 2 and the reaction orders for both reactions. The calculated results showed that the contributions of these two reactions to the total curing process were very different and changed with the heating rate. Except in the early cure stage, the calculated total degree of cure agreed well with the experimental data. Another method was based on the Borchardt and Daniels kinetic approach, where the activation energy of the cure reaction at each heating rate was determined separately. The whole curing process was modeled with one autocatalytic reaction. The fitting results showed that both preexponential factor and activation energy increased with the increment of the heating rate. As in the first method, the effect of heating rate on the orders of reaction was very small. The calculated results agreed well with experimental values in the early cure stage. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1911–1923, 2002     

环氧树脂固化反应动力学研究及其活性增韧

采用动态DSC法跟踪环氧树脂E-51／固化剂5784体系的反应历程,确定固化温度,利用Kissinger方程和Crane方程对固化反应动力学进行分析,通过红外分析确定聚硫橡胶的增韧方式,研究不同聚硫橡胶用量列固化产物力学性能的影响,采用扫描电镜分析试样断口形貌。研究结果表明：该固化体系的动力学参数为表观活化能△E=63．946kJ／mol,指前因子Ak=1．90×10^5,反应能级n=0．91,聚硫橡胶增韧环氧树脂通过化学键合来实现,并且效果明显。     

2-甲基咪唑/环氧树脂体系的固化动力学研究

利用等温DSC法对E-51环氧树脂/2-甲基咪唑(2-MI)体系的固化动力学进行了研究,拟合得到n级固化模型、自催化模型及Kamal复合模型方程中的各个参数值,以确定固化模型。研究表明:E-51/2-MI体系的固化过程分为2个阶段,即诱发阶段和加成反应,其固化反应兼具n级固化与自催化的特征,符合Kamal复合模型。     

氟橡胶-金属粘接用环氧胶固化动力学研究

采用具有高热变形温度的砜类聚合物制备的增粘剂,配制了可用于氟橡胶与金属粘接的环氧胶粘剂,通过凝胶时间的测定、差式扫描量热法(DSC)和傅立叶变换红外光谱(FTIR)研究了胶粘剂的固化反应过程及动力学。结果表明,胶粘剂在固化反应过程中有一个宽广且平缓的放热峰,对固化十分有利。胶粘剂固化反应表观活化能为63.8 kJ/mol,固化反应级数为0.891。     

Study on curing kinetics and curing mechanism of epoxy resin based on diglycidyl ether of bisphenol a and melamine phosphate

The curing kinetics of the diglycidyl ether of bisphenol A/melamine phosphate (DGEBA/MP) was analyzed by the DSC technique. The Kissinger and Flynn–Wall–Ozawa methods were applied to determine the dynamic kinetics of the DGEBA/MP system. The activation energies obtained by these two methods were 83.9 and 85.6 kJ/mol, respectively. An autocatalytic equation was applied to determine the isothermal curing kinetics of the DGEBA/MP system. The DGEBA/MP system exhibits autocatalytic behavior in the isothermal curing procedure, whose kinetics fits well with the autocatalytic mechanism. The obtained isothermal curing activation energy of the DGEBA/MP system was 110.0 kJ/mol. The curing mechanism of DGEBA with melamine phosphate was investigated using FTIR, ¹³C solid‐state NMR, and ³¹P solid‐state NMR. It involved an epoxide–amine reaction, etherification of phosphoric acid and epoxy, dehydration, and thermal oxidation of the hydroxyl group of the DGEBA/MP system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 892–900, 2004